Rope traction device

ABSTRACT

A rope traction device includes a sheave having an annular rope receiving groove and being driven and rotated with a traction rope received in the rope receiving groove to cause the traction rope to be wound on the sheave and the rope traction device thereby moves along the traction rope. The sheave includes a pair of side walls made of an elastic material and formed integrally with the sheave for formaing the rope receiving groove. The interval between inner surfaces of the side walls in a rope holding portion is made smaller than the diameter of the traction rope by a predetermined value. The rope receiving groove may be formed in a U-shaped section, a V-shaped section or a section which is a combination of the U-shaped section and the V-shaped section.

This is a divisional, of application Ser. No. 08/268,340, filed Jun. 30,1994 now U.S. Pat. No. 5,515,790.

BACKGROUND OF THE INVENTION

This invention relates to a rope traction device and, more particularly,to an improvement in a rope traction device suitable for use inconstruction, loading and unloading and conveying machines includingmoving scaffolds, elevators and craces.

A rope traction device is a type of winding instrument used forconstruction, loading and unloading and conveying machines and iscapable of moving up and down along a rope with the rope wound aroundits sheave by only one or few windings and without winding the ropearound and feeding it from a drum.

An example of a prior art rope traction device used for moving up anddown a moving scaffold for performing a work along an exterior wallsurface of a building is shown in FIG. 9. This rope traction deviceincludes a frame 1, a drive shaft 2 mounted on the frame 1, a motor (notshown) provided on the outer periphery of the drive shaft 2 through abearing and a sheave 4 driven by this motor. The rope traction devicefurther includes a traction mechanism 6 for holding a rope 5 wound aboutthis sheave 4 by one winding for preventing the rope 5 from slipping offthe sheave 4.

This traction mechanism 6 includes an L-shaped pivoting arm 8 providedin the vicinity of a point at which the rope 5 is disengaged from thesheave 4. A pair of roller 9, 9 are rotatably mounted at one end of thepivoting arm 8 to press the rope 5 inwardly from a straight tightenedstate thereof. Another pair of rollers 10, 10 are rotatably mounted on apivoting arm 11 which is pivotably mounted at the other end of thepivoting arm 8.

There is another type of prior art rope traction device disclosed inJapanese Patent Application Laid-open No. Hei 5-32395. In this ropetraction device, as shown in FIG. 10, side plates 13, 13 which come intocontact with the side surfaces of a rope 12 are made of leaf springseparately from a sheave main body 11. The two side plates 13, 13 areprovided at sides of the sheave main body 11 in such a manner that theinterval between the inner surfaces of the side plates is made smallerthan the diameter of the rope by a predetermined value and the sideplates 13, 13 are fixed to the sheave main body 11 by means of bolts 14alternately or at opposite positions in the circumferential direction ofthe sheave.

According to this prior art rope traction device, since the side platesmade of leaf springs are secured to the sides of the sheave by means ofbolts alternately in the circumferential direction of the sheave, andthe interval between the inner surfaces of the side plates is madesmaller than the diameter of the rope, when the rope is received betweenthe side plates, a portion of one of the side plates which is notsecured to the sheave by the bolt but is located on the opposite side ofa portion of the other side plate which is secured to the sheave by thebolt is flexed in the opposite direction to the portion of the sideplate which is secured to the sheave by the bolt, so that the respectiveside plates are flexed undulatingly in the circumferential direction. Asa result, a component force is produced due to the tension of the ropewhich component force is directed from the center of the rope to theportion of the side plate which is secured to sheave by the bolt andthis increases frictional force acting between the rope and the sideplates with the result that the pressing force excerted by the sideplates to the rope also increases whereby transmission of power from thesheave to the rope is efficiently performed. In the case where the sideplates are secured to the sides of the sheave by means of bolts atopposite positions in the circumferential direction, the rope receivedin the groove formed by the side plates is clamped and deformed so as toreduce its diameter in portions of the side plates which are secured tothe sheave at opposite positions by means of the bolts whereas portionsof the side plates which are not secured to the sheave are flexedoutwardly on both sides and, as a result, a wedging force acts on theportions of the side plates which are secured to the sheave by the boltsdue to the tension of the rope. As a result, frictional force actingbetween the rope and the side plates increases with resulting increasein the pressing force excerted by the sheave to the rope.

In the traction mechanism 6 of FIG. 9 in which the rope 5 is pressedagainst the sheave 4 by the pair of rollers 10, 10 mounted on thepivoting arm 11, bending moment is repeatedly applied to the rope 5 atpoints of contact with the V-shaped groove of the sheave 4 at twopositions at which the rollers 10, 10 tend to slip sideways by forceapplied in transverse direction by twisting of the rope 5. For thesereasons, wear occurs in the rope 5 and the life of the rope 5 thereby isshortened. Besides, change in the diameter of the rope 5 due to wear onthe rope 5 and the groove of the sheave 4 causes change in the state ofthe pivoting arm 8 before pivoting with resulting change and instabilityin the pressing force obtained by the movement of the rollers 9, 9 bythe rope 5, that is, the traction force.

In the rope traction device using the side plates 13 shown in FIG. 10,the flexion of the leaf springs applies stress concentrically atportions where the leaf springs are secured to the side plates, i.e.,fixing points by the bolts 14. Therefore, the bolts 14 and the portionsof the leaf springs about the openings for inserting the bolts 14therethrough must have sufficient strength. The leaf springsconstituting the side plates 13 must therefore have thicknesscorresponding to the strength of the portions about these openings wherestress is concentrically applied and thus require a large thickness.This requirement for large thickness of the leaf springs, together withthe requirement for mounting of the bolts 14, necessitates increase inthe weight of the rope traction device as a whole with resultingdifficulty in realizing a small and light-weight rope traction device.Moreover, the large thickness of the leaf springs increases the pressingforce of the leaf springs against the rope 12 and this results inshortening of the life of the rope 12. Moreover, the large thickness ofthe leaf springs reduces the amount of flexion of the leaf springs whichin turn reduces the rope holding force of the leaf springs.

In the prior art rope traction device of FIG. 10 in which the leafsprings are secured to the sheave main body 11 by means of the bolts 14,assembling and maintenance of the leaf springs are time-consuming andtroublesome and, besides, manufacturing of the leaf springs and formingof the openings for the bolts in the side plates 13 and the sheave mainbody 11 also increases the manufacturing cost of the rope tractiondevice.

Furthermore, since the side plates 13 are made of the leaf springs andit is extremely difficult to process the surface of the leaf spring bymachining, it is extremely difficult to obtain a rope groove having adesired sectional shape such as a tapered groove by the side plates 13.

It is, therefore, an object of the invention to provide a rope tractiondevice capable of prolonging the life of a wire rope with minimum wearcaused thereon.

It is another object of the invention to provide a rope traction devicecapable of achieving a stable traction force.

It is another object of the invention to provide a small andlight-weight rope traction device with a simplified structure.

It is another object of the invention to provide a rope traction devicein which a rope receiving groove of any desired sectional shape can bedesigned.

SUMMARY OF THE INVENTION

For achieving the above described object of the invention, there isprovided a rope traction device including a sheave having an annularrope receiving groove which sheave is driven and rotated with a tractionrope received in the rope receiving groove to cause the traction rope tobe wound on the sheave and said rope traction device thereby movingalong the traction rope characterized in that said sheave of the ropetraction device comprises a pair of side walls made of an elasticmaterial and formed integrally with the sheave for forming the ropereceiving groove, the interval between inner surfaces of the side wallin a rope holding portion being made smaller than the diameter of thetraction rope by a predetermined value.

According to the invention, when the rope is pushed in the ropereceiving groove of the sheave, the side walls elastically press therope on both sides thereof to produce frictional force and thereby holdthe rope, transmitting the power from the sheave to the rope. The ropetherefore can be pressed uniformly along the entire periphery of thesheave. Rollers for pressing the rope as in the prior art rope tractiondevice shown in FIG. 9 can therefore be obviated whereby the ropetraction device can be made smaller and lighter. Further, no bendingmoment is applied to the rope and no slippage of the rope due to forceacting in the transverse direction takes place so that wear of the ropecan be minimized and the life of the rope can be prolonged.

As compared with the rope traction device discloses in the abovedescribed Japanese Patent Application Laid-open No. Hei 5-32395 in whichthe side plates made of leaf springs are secured to the sheave by meansof the bolts, the side walls forming the rope receiving groove in thedevice according to the invention are made of an elastic material andformed integrally with the sheave and no bolts are used for securing theside wall portions to the sheave and, hence, no stress is appliedconcentrically at the fixing points by the bolts as in the prior artdevice but stress is applied uniformly along the entire periphery of theside walls forming the rope receiving groove. Since this uniform stressis much smaller than the stress applied concentrically at the fixingpoints by the bolts as in the prior art device, the thickness of theside walls of the sheave in the device according to the invention can bemade much smaller than the thickness of the leaf springs in the priorart device. This contributes, together with omission of the bolts, to adesign of a smaller and lighter rope traction device. Further, since therope is pressed uniformly along the entire periphery of the sheave, thelife of the rope can be prolonged and a stable rope holding force can bemaintained.

Further, as compared with the device disclosed in Japanese PatentApplicatinn Laid-open No. Hei 5-32395, no bolts are used fur securingside wall portions to sheave in the device according to the inventionand, therefore, assembling and disassembling as well as maintenance ofthe sheave are easy. Moreover, since no processing of the sheave such asmachining of bolt holes is obviated, the manufacturing process issimplified and the manufacturing cost is reduced.

Moreover, since the side walls forming the rope receiving groove is madeintegrally with the sheave, the side walls of the sheave can be formedsimply by grinding of a disk-like steel and hence a rope receivinggroove of any desired sectional shape such as one having a taperedsurface can be easily formed.

Preferred embodiments of the invention will be described below withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings,

FIG. 1 is a perspective view showing a sheave used in an embodiment ofthe invention;

FIG. 2 is a side view of the sheave with its upper half portion being aview taken along lines B--B in FIG. 3;

FIG. 3 is a front view of the sheave;

FIG. 4 is a view showing the rope traction device of this embodimentwith a part thereof being shown in section;

FIG. 5 is a view taken along lines A--A in FIG. 4;

FIGS. 6A and 6B are partial sectional views of an example of the ropereceiving groove formed in the sheave;

FIGS. 7A and 7B are partial sectional views of another example of therope receiving groove;

FIGS. 8A and 8B are partial sectional views of another example of therope receiving groove;

FIG. 9 is a sectional view showing a prior art rope traction device; and

FIG. 10 is a perspective view showing another example of a prior artrope traction device.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1 to 5, a rope traction device 15 has an annularsheave 20 provided in a frame 16. The sheave 20 has an annular ropereceiving groove 23 for receiving a wire rope 22 formed along theperipheral surface of the sheave 20.

This sheave 20 has an annular recess 20a (see FIG. 2) formed in theinner peripheral portion on one side of the sheave 20. A central opening20b is formed contiguously to the annular recess 20b. As shown in FIG.4, a stepped portion 50a formed in the front portion of a disk-likesheave holding member 50 is fitted in the annular recess 20a and thecentral opening 20b and the sheave 20 is secured to the sheave holdingmember 50 by means of bolts 51 inserted in bolt holes 20c formed in acircumferential direction in the inner peripheral side of the sheave 20.This sheave holding member 50 is rotatably supported on the frame 19through a bearing 58.

For guiding a rope 22 accurately into the sheave 20, guide rollers 53,54 and 55 are provided on the frame 16 as shown in FIG. 5. There is alsoprovided a dust removing tongue 56 on the frame 16 for preventingintrusion of dust into the rope receiving groove.

The sheave 20 is driven by a drive mechanism (not shown) including adrive shaft 57 (FIG. 5). Since this drive mechanism is well known in theart, description thereof will be omitted.

As the sheave 20 is driven by the unillustrated drive mechanism, therope 22 which is wound on the sheave 20 by about one winding is receivedin the rope receiving groove 23 by the guide rollers 53 through 55mounted on the frame 16 and the rope 22 is pressed on the entireperiphery thereof by side walls 24 which, together with the peripheralsurface portion of the sheave 20 between the side walls 24, form therope receiving groove 23 whereby the drive power is transmitted from theside walls 24 to the rope 22.

When a hanging load is applied to the rope 22, the rope 22 is engagedtightly in the rope receiving groove 23 due to tension produced by thehanging load and the drive power is transmitted from the sheave to therope.

FIGS. 6A, 6B, 7A, 7B, 8A and 8B are partial sectional views of someexamples of the shape of the the rope receiving groove 23.

FIG. 6A shows an example in which the rope receiving groove 23 is formedin a substantially U-shaped section. The two side walls 24, 24 areformed integrally with the sheave 20 and made of an elastic material.e.g., SUS 420J2 stainless steel. Inner surfaces 24a, 24a of the sidewalls 24, 24 which come into contact with the rope 22 are formed inplanes which are parallel to each other and are extending in the radialdirection of the sheave 20. A bottom surface 25 of the rope receivinggroove 23 is formed substantially in the shape of a semi-circle. Theinterval A between the inner surfaces 24a, 24a of the side walls 24, 24is set at a value which is smaller than the diameter D of the rope 22 bya predetermined value.

When the rope 22 is pushed in the rope receiving groove 23 by the guideroller 53 or due to the tension produced by hanging load, the side walls24, 24 made of the elastic material are pushed apart as shown in FIG. 6Bso that the rope 22 is brought into contact with the inner surfaces 24a,24a of the side walls 24, 24 and the bottom surface 25 of the sheave 20.A frictional force F is produced uniformly between the rope 22 and theside walls 24, 24 which clamp the rope 22 on both sides thereof to holdthe rope 22 and the drive power is transmitted from the sheave 20 to therope 22.

In this embodiment, increased frictional force between the rope 22 canbe obtained due to the contact of the rope 22 with the bottom surface 25in addition to the inner surfaces 24a, 24a of the side walls 24, 24.Besides, since the rope 22 is not displaced in the radial direction inthe rope receiving groove 23, the diameter of winding of the rope 22 isconstant and, accordingly, a uniform running speed of the rope 22 can beachieved.

FIG. 7A shows an example in which the rope receiving groove 23 is formedin a substantially V-shaped section. Inner surfaces 24a, 24a of sidewalls 24, 24 forming the rope receiving groove 23 are formed in inclinedsurfaces defining a radially outwardly enlarging taper T. A bottomsurface 25 is formed in a substantially flat surface. The interval Abetween the inner surfaces 24a, 24a of the side walls 24, 24 at a ropeholding position is set at a value which is smaller than the diameter Dof the rope 22 by a predetermined value. Assuming that the depth of therope receiving groove 23 is set at 15 mm, the interval between the innersurfaces 24a, 24a at the outer ends of the side walls 24, 24 at 7.8 mmand the thickness of the side wall 24 at its outer end at 2.5 mm, anoptimum taper T is about 10 degrees.

When the rope 22 is pushed in the rope receiving groove 23, the sidewails 24, 24 are pushed apart as shown in FIG. 7B and the rope 22 isbrought into contact with the inner surfaces 24a. 24a of the side walls24, 24. A clamping force pressing the rope 22 uniformly on both sidesthereof acts in the pushed apart side walls 24, 24 and, in addition, awedging force is applied on the rope 22 due to the tapered innersurfaces 24a, 24a. A frictional force F which is a resultant complexforce of these forces is applied to the rope 22 which is thereby held inthe rope receiving groove 23.

FIG. 8A shows an example in which the rope receiving groove 23 is formedin a section which is a combination of the V-shaped section and theU-shaped section. Inner surfaces 24a, 24a of side walls 24, 24 whichcome into contact with the rope 22 are formed in inclined surfaceshaving a radially outwardly enlarging taper T and a bottom surface 25 isformed substantially in the shape of a semi-circle. The interval Abetween the inner surfaces 24a, 24a at a middle rope holding position isset at a value which is smaller than the diameter D of the rope 22 by apredetermined value.

When the rope 22 is pushed in the rope receiving groove 23, the sidewalls 24, 24 are pushed apart as shown in FIG. 8B and the rope 22 isbrought into contact with the inner surfaces 24a, 24a of the side walls24, 24 and the bottom surface 25. A clamping force pressing the rope 22on both sides thereof acts in the pushed apart side walls 24, 24 and awedging force caused by the tapered inner surface 24a, 24a is produced.Thus, a frictional force F which is a resultant complex force of theseforces is applied to the rope 22. The increased frictional force due tothe contact of the rope 22 with the bottom 25 and the constant diameterof winding of the rope 22 enable the rope traction device to achieve auniform running speed of the rope 22.

In the examples of FIGS. 7A and 8A in which the rope receiving groove 23is formed substantially in a V-shaped section, when the diameter of therope 22 is reduced due to wear or pretension, the rope 22 can still pushthe side walls 24, 24 apart at a deeper position in the groove 23 thanwhen the diameter is not reduced and, accordingly, a rope clamping forcewhich is substantially equivalent to the case where the diameter of therope 22 is not reduced can be produced. Therefore, in the case of therope receiving groove of the V-shaped section, a constantly stable ropetraction force can be obtained even when the diameter of the rope haschanged whereby reliability of the device is enhanced. In comparison, inthe prior art device shown in FIG. 9, even if the rope receiving grooveis formed in a V-shaped section, change in the rope diamter brings aboutchange in the amount of rotation of the pivoting arm with resultingchange in the rope pressing force by the rollers so that a constantlystable traction force cannot be obtained.

What is claimed is:
 1. A rope traction device including a sheave having an annular rope receiving groove which sheave is driven and rotated with a traction rope made of a wire rope having a fixed diameter and a substantially circular cross-section which is received in said rope receiving groove to be wound on said sheave and thereby moving along said traction rope, said rope traction device being characterized in that said sheave of said rope traction device comprises a pair of side walls which come into contact with said wire rope and are formed integrally with said sheave to form said rope receiving groove, said rope receiving groove being formed in a combination of a V-shaped section and a U-shaped section with the inner surfaces of said side walls which come into contact with said wire rope being formed in inclined surfaces that define a radially, outwardly enlarging taper, said rope receiving groove having a bottom surface which is substantially in the shape of a semi-circle, the distance between the inner surfaces of said side walls in a rope holding position being made smaller than said diameter of said wire rope by a predetermined value when said wire rope is not received in said rope receiving groove and said side walls being made entirely of a material having such elasticity that, said side walls are elastically pushed apart to receive and clamp said wire rope at said rope holding position.
 2. A rope traction device including a sheave having an annular rope receiving groove which sheave is driven and rotated with a traction rope made of a wire rope having a fixed diameter and a substantially circular cross-section which is received in said rope receiving groove to be wound on said sheave and thereby moving along said wire rope, said sheave being a single sheave having a pair of side walls, which come into contact with said wire rope, said pair of side walls being formed integrally with said sheave to form said rope receiving groove, said rope receiving groove being formed of a combination of a V-shaped section and a U-shaped section with the inner surfaces of said side walls which come into contact with said rope being formed in inclined surfaces that define a radially, outwardly enlarging taper said rope receiving groove having a bottom surface which is substantially in the shape of a semi-circle, the distance between the inner surfaces of said side walls in a rope holding position which is made smaller than said diameter of said wire rope by a predetermined value when said wire rope is not received in said rope receiving groove and said sheave being made entirely of a material having such elasticity that, said side walls are elastically pushed apart to receive and clamp said wire rope at said rope holding position. 